Powered accumulating conveyors are utilized wherever sorting, handling, processing, or other considerations, require that the conveyed items either (1) be stopped, or (2) bunched up, before proceeding down the conveyor bed. Conventional accumulating conveyors, which may be a hundred or more feet in length, are usually divided into "zones" that are nominally thirty-six inches in length. Each zone has a mechanism, such as a sensor roller, a mechanical trigger, a pneumatic switch, a photodetector, etc. that engages, and disengages, the driving power to the rollers of the preceding zone. When an accumulation operation is initiated, an external signal (which may be provided manually by a human operator or automatically by a timer control, or a computer program) disengages the rollers of the last, or discharge, zone. When the next item travelling down the conveyor bed depresses the sensor in the discharge zone, the sensor disengages the drive mechanism in the preceding upstream zone. When an item contacts the sensor in the preceding upstream zone, the process is repeated, in a series of steps, in each preceding upstream zone.
To illustrate, U.S. Pat. No. 3,612,248, granted Oct. 12, 1971, to Charles W. Wallis, discloses an accumulating roller conveyor comprising a plurality of longitudinally spaced, transversely extending article carrying rollers 10 with a belt 11 positioned beneath the rollers. Pressure rollers 12 are normally held in position against the belt to press the belt against the article carrying rollers by expansible chambers (30) to which fluid is supplied. A fluidic switch (16) is provided along the path of the articles, and when an article is stopped in position overlying the switch, the fluidic switch functions to deflate the expansible Chamber, permitting the pressure rollers to move away from the belt, so that rotation of the article-carrying rollers is interrupted.
U.S. Pat. No. 3,768,630, granted Oct. 30, 1973 to R. A. Inwood et al, discloses a powered roller accumulator conveyor having a powered propelling member, such as belt 16, passing through a plurality of independent accumulating zones (zones A, B, C, etc.) arranged along the conveyor. The propelling member is shiftable between driving, and non-driving, positions (compare FIGS. 3 and 4), with respect to the powered rollers 14 by vertically. shiftable, supporting rollers 18, operated by pneumatically powered actuators, such as tube-like member 30 and support plate 32, that engage one end of shaft 20 for roller 18. Each actuator is controlled by a series of valves 100 connected to a source 122 of fluid pressure, as shown schematically in FIGS. 7 and 8.
In the accumulating position of FIG. 7, each actuator is connected through an article-detecting sensor-operated valve 44 to the source of fluid pressure. The plunger 66 of valve 44 is influenced by sensor roller 49 that pivots flange 58 relative to the plunger, when a parcel contacts the roller. The shank 99 of the plunger 66 cooperates with ball valve 86 to control the flow of fluid away from the actuator 30. Each sensing assembly 46 is biased upwardly by spring 62 above the plane of the pressure rollers to be contacted by each object moving along the accumulator conveyor, as shown in FIG. 2. In an override or discharge position, shuttle valves 100 associated with each actuator are series connected to the source of fluid pressure, through a main control valve (such as three-way valve 131). The valves and are operative to direct the flow of fluid from the sensor operated valve 44, to energize each of the actuators 30, in each of the zones, to shift all of the operating zones into driving position.
U.S. Pat. No. 3,840,110, granted Oct. 8, 1974, to R. P. Molt et al, discloses a live roller, zero pressure accumulation conveyor 11, including a drive shaft 16 and a plurality of axially aligned countershafts 20. Each countershaft is driven by the drive shaft through a clutch 25 for selective power transmission to individual groups of conveyor rollers 14. Each group of rollers has, at its downstream end, a trigger device 51 (FIGS. 8 and 9) which senses the presence of a conveyed article. The trigger devices, which are operatively associated with air valves 52, 53, operate to selectively engage, and disengage, the clutch associated therewith, to achieve, and maintain, the desired spicing between articles being transported on the conveyor. Preferably, dual trigger devices (51x; 51y) are used in a manner which requires coincident actuation of both trigger devices before the clutch associated with a given group of rollers is disengaged (note column 3, line 63--column 4, line 5).
U.S. Pat. No. 4,108,303, granted Aug. 22, 1978, to R. K. Vogt and M. A. Heit, discloses an accumulator conveyor that includes a plurality of article accumulating zones A-E extending between the infeed and discharge ends of the conveyor. Each zone of the conveyor includes at least one power transmission assembly 17. All of the assemblies are powered by a single flexible drive member, such as an endless chain 56a, 56b. Each power transmission assembly includes a fluid ram 36, with a flexible diaphragm 58, which cooperates with a power wheel 37 to move that power wheel into, and out of, driving engagement with the article propelling member(s), such as rollers 11, within the zone that it serves. Operation of the transmission assemblies is controlled by a fluid control circuit 80. The fluid control circuit is influenced by sensor devices 18, which provide sensor valve 33, with a mechanical signal indicating whether, or not, an article is present, or absent, from a particular zone; the signal activates, or deactivates, the transmission assemblies 17 within the zone. As shown in FIG. 1, each sensor device 18 includes a sensor roller 19, a bracket 20, and a spring 28 for urging the sensor device to an operative position slightly above the plane of the upper surface of the rollers and/or roller bed.
Other accumulator conveyors are disclosed in U.S. Pat. No. 4,109,783, granted Aug. 29, 1978, to Robert K. Vogt; in U.S. Pat. Nos. 4,344,527 and 4,473,149, granted to Robert K. Vogt and Martin A. Heit, on Aug. 17, 1982 and Sep. 25, 1984, respectively.